Fixing eccentric diameters

admin

You get some odd setups in the machine shop and thought some of this repair might be useful. I just posted 2 videos of eccentric turning. These date to last May but I've been working through a computer bust and new build and am just getting around to things.The first vid is snipped down to 5 min. but shows what turning with offset pots looks like. I also took a finishing cut as if I were going to file or polish for size instead of grinding like usual.The second vid is another way of working to very close dimensions with an engine lathe. The toolbit is what they call a "contrary grind", similar the way a shaper bit is ground for fine finish. A boring tool is more complicated to do this with but works super with hard to finish materials. I usually try to finish .0005" oversize and then stone the diameter, not polish with paper, if I have to do things this way. Anyway...(edit) I forgot to add, "DON'T GRAB THE CHIPS" if you do this! Also there are stills at the end showing the toolbit compared to a normal tool, and a picture of the turned shaft over a ground one for comparison.I have recordings of the setups, layouts etc. of all this I just have to find and get through & will post as they are done.MattLast edited by Matt_Maguire; 10-09-2011 at 01:32 PM.
Reply:thanks for posting those Matt. I'm taking a basic metal turning class this fall at one of the local tech schools. Your vids probably showed me more than I've picked up so far this semester..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Looks great. You've got more rake on your contrary ground bit than I've got on mine. I'll have to try that sometime. Yeah the chips that come off are a little on the sharp side. Millermatic 252XMT 304'sDynasty 280DXHypertherm PowerMax 1250Miller Trailblazer 302 EFIOptima PulserXR feeder and XR Edge gun and more athttp://members.dslextreme.com/users/waynecook/index.htm
Reply:I finished another video. This is how I find the offset axis and the amount of offset. For one part, all of this can be done in a machine if you have the ability to offset each end like a crankshaft grinder or a bearing mounted chuck for the tailstock on the lathe or have pots like I use.I had something like 30 diameters then, it takes a few minutes each to layout and reference when I'm not explaining and talking while working. I also have to confess to a regression in the next post where I indicate the part for turning that took much longer than I used to do it... Because I decided to change things a bit...   Enough chatter, here's the video; Originally Posted by DSWthanks for posting those Matt. I'm taking a basic metal turning class this fall at one of the local tech schools. Your vids probably showed me more than I've picked up so far this semester.
Reply:Got some more done. This video reveals a serious regression in set up time on the lathe. Fooling around with the laser for reference instead of just leveling the jaws and setting up a jack screw to the ways which can be quickly removed and replaced is embarrassing... You can use a scale or toolbit on center to reference the pot at the tailstock much quicker.I think it takes just about double the time using the laser, multiply that over 25 or so diameters, no wonder it took so long...[ame]http://www.youtube.com/watch?v=ZaVm1BouPGM[/ame]Matt